In the field of measuring trace components, particularly in the field of clinical diagnostics, measurement methods of applying principles of immunology are utilized and immunoassays using fine solid carriers as a solid phase are widely used. The fine solid carriers include erythrocytes, gelatin particles, latex particles and the like, and a quantitative analysis is performed by absorbing antigen or/and antibody on the surface thereof and reacting immunologically the antibody or/and the antigen against antigen or/and antibody in a test sample. It is well-known that the immunoassays using these fine solid carriers are also commonly used even in the fields other than clinical diagnosis.
Chemiluminescence measurement utilizing chemiluminescence reaction in which the chemiluminescence is caused by allowing an enzyme such as alkaline phosphatase to act upon a chemiluminescent substrate such as 1,2-dioxetanes can rapidly and sensitively measure the presence or concentration of a measurement subject in a specimen, and has been widely used to measure viruses such as HIV and HCV, and other trace components in vivo (JP 96-507694).
It is well-known that a quenching reaction occurs in a liquid medium, particularly in an aqueous medium with chemiluminescence by decomposition of chemiluminescent substrate having dioxetane. Many test samples are biological samples in general, and thus the measurement of the samples by such a method is generally performed in an aqueous medium. Therefore, the quenching reaction sometimes reduces substantially the chemiluminescence occurred by the decomposition of the chemiluminescent substrate having dioxetane, which is actually obsereved. In the measurement methods of certain test samples, e.g., nucleic acids, a viral antibody and other proteins, in which a detection at a low level is required, the chemiluminescence reduced by the quenching reaction in combination with unavoidable background signals reduces the sensitivity of the measurement method, and thus in some cases, those at an extremely low level can not be detected. In order to improve these quenching reactions, an addition of a water soluble macromolecule including both naturally occurring and synthetic molecules (see U.S. Pat. No. 5,145,722), an addition of various water soluble enhancers to test samples (see U.S. Pat. No. 4,978,614), or water soluble polymerized quaternary ammonium salts such as poly(vinylbenzyltrimethyl ammonium chloride) (TMQ), poly(vinylbenzyltributyl ammonium chloride) (TBQ) and poly(vinylbenzyldimethylbenzyl ammonium chloride) (BDMQ) as the water soluble polymerized quaternary ammonium salts has been used (see U.S. Pat. No. 5,112,960 and JP 8-507694 T).
In the meanwhile, the chemiluminescence enhancers such as TMQ, TBQ and BDMQ described above are polymers with high molecular weight. In the case of being used for a signal detection in a solid phase immunoassay using antigen or/and antibody immobilized onto a fine solid carrier dispersible in a liquid medium, when the carriers are once physically aggregated, for example, in order to wash after an immune reaction, these polymers prevent the fine solid carriers from dispersing thereafter, inhibit luminescence caused by an enzymatic reaction of the chemiluminescent substrate having dioxetane depending on the concentration of the subject substance to be detected, and have sometimes had a problem in that no precise measurement value can be obtained.